Command-line substitution can be used anywhere on the gnuplot command line, except inside strings delimited by single quotes.
Example:
This will run the program leastsq and replace leastsq (including
backquotes) on the command line with its output:
f(x) = `leastsq`
or, in VMS
f(x) = `run leastsq`
These will generate labels with the current time and userid:
set label "generated on `date +%Y-%m-%d` by `whoami`" at 1,1 set timestamp "generated on %Y-%m-%d by `whoami`"